The syntheses of BOC-Leu-delta Leu.OH and BOCHis-delta Leu.OH are underway. Each peptide will be incorporated into an octapeptide: His-Pro-Phe-His-Leu-delta Leu-Val-Tyr.OH and His-Pro-Phe-His-Leu-delta-Val-Tyr.OH, respectively. These renin substrate analogs will be tested as renin inhibitors.